The Introduction of Solid Phase Extraction Technology
Solid Phase Extraction (SPE) technology was developed in the 1970s. Due to its high efficiency, reliability, and low consumption of reagents, it has replaced traditional liquid-liquid extraction in many fields and has become an effective means of sample preparation.
Some of the traditional books on SPE attribute it to the principle of liquid chromatography, which is actually one of the main sources of improper use. Think of the SPE cartridge as a liquid chromatography column. It is better to think of it as a simple extractant because the focus of liquid chromatography is on separation, while the focus of SPE is on extraction.
The role of solid phase extraction in sample processing is divided into two types, purification, and enrichment. These two effects may exist simultaneously.
Compared with liquid-liquid extraction, the advantages of solid extraction are that it is convenient and consumes fewer reagents. The shortcoming is that the repeatability between batches is difficult to guarantee. The reason for this is that the reproducibility of the liquid reagent is good, and the physicochemical properties of the products of different ages are reliable as long as the purity is reliable. However, even if the solid extractant guarantees purity, there are differences in particle size, differences in shape, and other factors that are not present and difficult to measure. The extraction properties of different batches may be different in different years.
Theoretically and by manufacturers, solid phase extraction should be well applied in the pretreatment of chromatographic analysis: organic solvents are used very little, and samples can be processed in batches, which can be enriched and decontaminated. The impression is a revolutionary advancement in pre-processing. However, the reality is at least in China. Although it has been promoted for many years, the practical application is quite limited.
Solid phase extraction can be a good supplement to the pretreatment method, but when using it, be sure to know its advantages and disadvantages, pay attention to local conditions, and avoid weaknesses.
The application advantages of solid phase extraction
In the pre-treatment of any project, it is suitable to use solid phase extraction technology, that is, solid phase extraction is more ideal than ordinary solvent extraction.
1. Pretreatment of organic matter in water.
Such conventional treatment is basically oscillating extraction with an organic solvent which is incompatible with water, and the advantage of solid phase extraction is that
a. The pre-processing can be repeated quantitatively.
Solvent oscillation operation generally only requires the degree of control time, but can not control the oscillation frequency, intensity, and action. We know that each person’s oscillation action is different, that is, the same person, it is difficult to ensure that the action is always uniform. Therefore, the action of solvent extraction is not quantitative and cannot be repeated.
In the case of solid phase extraction, it is easier to maintain the uniformity and stability of the column and the elution rate. Therefore, the extraction process of the solid phase extraction can be repeated and quantifiable.
b. On-site processing.
The analysis of organic matter in water has a bottleneck that has long plagued us. That is to say, organic matter can remain relatively stable in ponds and reservoirs, etc., but once it enters the small environment of the sampling bottle, it will change rapidly. Therefore, many water organic matter analysis methods require immediate analysis, and the maximum can not exceed 4 hours. The general situation is that the time from the water withdrawal to the laboratory is far more than 4 hours, the sample has changed, and the reliability of the analysis results can be imagined.
If the solid phase extraction technology is introduced, since it is simple in equipment, small in size, and easy to carry, it can be sampled at the site and pretreated. The sampler brought back to the lab was a solid phase extraction column instead of a water sample. This will ensure that we are dealing with water samples that are truly stable.
From practical applications, the use of solid phase extraction technology to replace traditional liquid-liquid extraction in the detection of water still has considerable work to be explored. It is not completely replaced at present, but its development prospects are worthy of optimism.
c. Reduction in the consumption of organic reagents.
When using a solid phase extraction, it is only necessary to use an organic solvent at the time of elution, which is a little more than ten times that of conventional liquid-liquid extraction. It has a positive significance for the personal protection and environmental protection of the experimenter.
2. Pharmaceutical ingredient extraction of bulk biomaterials
This is an example of the success of solid phase extraction in practical applications. It mainly refers to the pretreatment work when testing blood samples and urine samples in hospitals. Because the adsorption of drug components is the advantage of solid phase extraction, plus the sample is single, and the composition Fixed, it is very suitable for large-scale batch purification operation after determining the method.
3. Immunoaffinity solid phase extraction.
The ideal state of extraction is specific enrichment or specific repellent, but whether it is solvent extraction or solid phase extraction, it is basically similarly soluble, and at most, it can achieve “a certain type of level” of extraction, but cannot reach “some A “level of extraction.
Adding immunoaffinity technology to the solid phase extraction column can make use of its biospecific selective adsorption to achieve a near-theoretical perfect extraction.
The practical difficulty is that although the concept is very good, it is less available due to the relatively high technical difficulty.